Digital generator for producing a sinewave
US4285044A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 11, 1979 |
| Grant date | Aug 18, 1981 |
| Priority date | — |
| Expiry date | Jul 11, 1999 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2101/04
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A digital sinewave generator can be used in digital equipment, e.g. instead of a local oscillator for modulation/demodulation of signals. If there is no simple relationship between sampling rate and the frequency of the sinewave, successive sample values must be calculated since storage of these values would be prohibitive. For a sinewave Re.sup.jk.phi. sampled at successive instants k=0, 1, 2, . . . etc. separated by a phase angle .phi., quadrature components A.sub.k +jB.sub.k =Re.sup.jk.phi. can be calculated using the algorithm: EQU A.sub.k+1 =cos.phi.A.sub.k -sin.phi.B.sub.k EQU B.sub.k+1 =sin.phi.A.sub.k +cos.phi.B.sub.k. Unfortunately it is impossible for cos.sup.2 .phi.+sin.sup.2 .phi. to be exactly equal to unity if calculations are performed with finite precision using an even number base, which as the effect of causing the modulus of a sinewave generated by this algorithm to tend exponentially to 0 to .infin.. The present invention overcomes this by using the above algorithm to obtain approximations A.sub.k+1 ' and B.sub.k+1 ' to the desired result at terminals (9 and 10) and then multiplying (22,23) the approximations A.sub.k+1 ' and B.sub.k+1 ' by a correction factor ( …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.